Detection of Field Winding Faults in Synchronous Motors via Analysis of Transient Stray Fluxes and Currents

(c) 2021 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.[EN] The detection of rotor failures in synchronous motors is a matter of primordial interest in many industrial sites where these machines are critical assets. However, due to the particular operation of these motors, most conventional techniques relying on steady-state analysis, commonly used in other electric machines, are not applicable to such motors. In this context, it has been recently proven that the analysis of different quantities under transient operation of the motor and, more specifically, under motor starting can provide crucial information for the diagnosis of many faults. This work proposes the time-frequency analysis of stray fluxes and currents to detect field winding faults in synchronous motors. The potential consequences of this fault can be catastrophic for the motor integrity, so that the detection of its presence in its early stages can be of critical importance for the industry. The results included in this paper prove the usefulness of the transient analysis of such non-invasive quantities not only to detect the presence of the field winding fault but also to set a starting point to determine its severity.This work was supported by the Spanish Ministerio de Ciencia Innovación y Universidades and FEDER program in the framework of the Proyectos de I+D de Generación de Conocimiento del Programa Estatal de Generación de Conocimiento y Fortalecimiento Científico y Tecnológico del Sistema de I+D+i, Subprograma Estatal de Generación de Conocimiento (ref: PGC2018-095747-B-I00).Tian, P.; Antonino Daviu, JA.; Platero, C.; Dunai, L. (2021). Detection of Field Winding Faults in Synchronous Motors via Analysis of Transient Stray Fluxes and Currents. IEEE Transactions on Energy Conversion. 36(3):2330-2338. https://doi.org/10.1109/TEC.2020.3041643S2330233836

Comparison of BES measurements of ion-scale turbulence with direct, gyrokinetic simulations of MAST L-mode plasmas

Observations of ion-scale (k_y*rho_i <= 1) density turbulence of relative amplitude dn_e/n_e <= 0.2% are available on the Mega Amp Spherical Tokamak (MAST) using a 2D (8 radial x 4 poloidal channel) imaging Beam Emission Spectroscopy (BES) diagnostic. Spatial and temporal characteristics of this turbulence, i.e., amplitudes, correlation times, radial and perpendicular correlation lengths and apparent phase velocities of the density contours, are determined by means of correlation analysis. For a low-density, L-mode discharge with strong equilibrium flow shear exhibiting an internal transport barrier (ITB) in the ion channel, the observed turbulence characteristics are compared with synthetic density turbulence data generated from global, non-linear, gyro-kinetic simulations using the particle-in-cell (PIC) code NEMORB. This validation exercise highlights the need to include increasingly sophisticated physics, e.g., kinetic treatment of trapped electrons, equilibrium flow shear and collisions, to reproduce most of the characteristics of the observed turbulence. Even so, significant discrepancies remain: an underprediction by the simulations of the turbulence amplituide and heat flux at plasma periphery and the finding that the correlation times of the numerically simulated turbulence are typically two orders of magnitude longer than those measured in MAST. Comparison of these correlation times with various linear timescales suggests that, while the measured turbulence is strong and may be `critically balanced', the simulated turbulence is weak.Comment: 27 pages, 11 figure

Human interaural time difference thresholds for sine tones: The high-frequency limit

[EN] The smallest detectable interaural time difference (ITD) for sine tones was measured for four human listeners to determine the dependence on tone frequency. At low frequencies, 250 700 Hz, threshold ITDs were approximately inversely proportional to tone frequency. At mid-frequencies, 700 1000 Hz, threshold ITDs were smallest. At high frequencies, above 1000 Hz, thresholds increased faster than exponentially with increasing frequency becoming unmeasurably high justabove 1400 Hz. A model for ITD detection began with a biophysically based computational model for a medial superior olive (MSO) neuron that produced robust ITD responses up to 1000 Hz, and demonstrated a dramatic reduction in ITD-dependence from 1000 to 1500 Hz. Rate-ITD functions from the MSO model became inputs to binaural display models both place based and rate-differ-ence based. A place-based, centroid model with a rigid internal threshold reproduced almost all fea- tures of the human data. A signal-detection version of this model reproduced the high-frequence divergence but badly underestimated low-frequency thresholds. A rate-difference model incorporat- ing fast contralateral inhibition reproduced the major features of the human threshold data except for the divergence. A combined, hybrid model could reproduce all the threshold data.We are grateful to Dr. Les Bernstein for a useful discussion about the centroid display and to Dr. Steve Colburn for discussions about modeling. Zane Crawford provided valuable statistical help. This research was supported by The Vicerectorado de Profesorado y Ordenacion Academica of the Universitat Politecnica de Valencia (Spain), which brought L. D. to Michigan State, by the NIDCD Grant No. DC-00181 and the AFOSR Grant No. 11NL002. A. B. was supported by NIDCD Grant Nos. DC-00100 (H. S. Colburn) and P30-DC04663 (Core Center).Brughera, A.; Dunai ., L.; Hartmann, WM. (2013). Human interaural time difference thresholds for sine tones: The high-frequency limit. The Journal of the Acoustical Society of America. 133(5):2839-2855. https://doi.org/10.1121/1.4795778S28392855133

Measurement and physical interpretation of the mean motion of turbulent density patterns detected by the BES system on MAST

The mean motion of turbulent patterns detected by a two-dimensional (2D) beam emission spectroscopy (BES) diagnostic on the Mega Amp Spherical Tokamak (MAST) is determined using a cross-correlation time delay (CCTD) method. Statistical reliability of the method is studied by means of synthetic data analysis. The experimental measurements on MAST indicate that the apparent mean poloidal motion of the turbulent density patterns in the lab frame arises because the longest correlation direction of the patterns (parallel to the local background magnetic fields) is not parallel to the direction of the fastest mean plasma flows (usually toroidal when strong neutral beam injection is present). The experimental measurements are consistent with the mean motion of plasma being toroidal. The sum of all other contributions (mean poloidal plasma flow, phase velocity of the density patterns in the plasma frame, non-linear effects, etc.) to the apparent mean poloidal velocity of the density patterns is found to be negligible. These results hold in all investigated L-mode, H-mode and internal transport barrier (ITB) discharges. The one exception is a high-poloidal-beta (the ratio of the plasma pressure to the poloidal magnetic field energy density) discharge, where a large magnetic island exists. In this case BES detects very little motion. This effect is currently theoretically unexplained.Comment: 28 pages, 15 figures, submitted to PPC

Individual-active form of training of surgeons in their postgraduate education.

Training physicians at the courses not only should increase their general level of education in the specialty, but also provide opportunities for self-improvement through in-depth analysis of their practical activities and introduction of modern techniques and technologies into their own surgical practice. To implement this approach, we have improved the well-known methodology for conducting seminar sessions - the "round table". The main actors in individual seminars were the most experienced doctors. Each of them, if desired, chose the topic of the lesson, which best suited his specialization and work experience. The material was presented in the form of a presentation and consisted of the following main parts: introduction, theoretical and practical parts and conclusions. The most valuable was the practical part, in which the speaker presented his own results of diagnosis and treatment of the pathology that was being considered. Obligatory in this part of the presentation was the section "complications and mortality." The speaker analyzes the new methods of treatment he introduced personally, gives examples from his own practice and demonstrates data of laboratory, radiation, endoscopic diagnostics, photos and video materials. All doctors take part in the discussion. The teacher places the main accents and outlines the ways of further development of science in one or another direction. All 144 listeners who took part in this positively evaluated the innovation. At the same time, 106 (75%) of listeners defined positively the role of the teacher as a moderator of the educational process, and 119 (82,6%) indicated an increase in the motivational component. The fact of obtaining new knowledge and its practical importance was noted by 84 (58,3%) of the listeners. Comparative analysis of the traditional and proposed methods showed the advantage of the latter: 87,4% of positive responses to test assignments based on the proposed method of teaching, versus 71,3% for traditional ones. Thus, the improved “round table” method used has allowed to significantly improve the level of professional training of doctors and to increase the motivational component of lifelong learning

Individual-active form of training of surgeons in their postgraduate education.

Training physicians at the courses not only should increase their general level of education in the specialty, but also provide opportunities for self-improvement through in-depth analysis of their practical activities and introduction of modern techniques and technologies into their own surgical practice. To implement this approach, we have improved the well-known methodology for conducting seminar sessions - the "round table". The main actors in individual seminars were the most experienced doctors. Each of them, if desired, chose the topic of the lesson, which best suited his specialization and work experience. The material was presented in the form of a presentation and consisted of the following main parts: introduction, theoretical and practical parts and conclusions. The most valuable was the practical part, in which the speaker presented his own results of diagnosis and treatment of the pathology that was being considered. Obligatory in this part of the presentation was the section "complications and mortality." The speaker analyzes the new methods of treatment he introduced personally, gives examples from his own practice and demonstrates data of laboratory, radiation, endoscopic diagnostics, photos and video materials. All doctors take part in the discussion. The teacher places the main accents and outlines the ways of further development of science in one or another direction. All 144 listeners who took part in this positively evaluated the innovation. At the same time, 106 (75%) of listeners defined positively the role of the teacher as a moderator of the educational process, and 119 (82,6%) indicated an increase in the motivational component. The fact of obtaining new knowledge and its practical importance was noted by 84 (58,3%) of the listeners. Comparative analysis of the traditional and proposed methods showed the advantage of the latter: 87,4% of positive responses to test assignments based on the proposed method of teaching, versus 71,3% for traditional ones. Thus, the improved “round table” method used has allowed to significantly improve the level of professional training of doctors and to increase the motivational component of lifelong learning

Aerodynamic investigations of ventilated brake discs.

The heat dissipation and performance of a ventilated brake disc strongly depends on the aerodynamic characteristics of the flow through the rotor passages. The aim of this investigation was to provide an improved understanding of ventilated brake rotor flow phenomena, with a view to improving heat dissipation, as well as providing a measurement data set for validation of computational fluid dynamics methods. The flow fields at the exit of four different brake rotor geometries, rotated in free air, were measured using a five-hole pressure probe and a hot-wire anemometry system. The principal measurements were taken using two-component hot-wire techniques and were used to determine mean and unsteady flow characteristics at the exit of the brake rotors. Using phase-locked data processing, it was possible to reveal the spatial and temporal flow variation within individual rotor passages. The effects of disc geometry and rotational speed on the mean flow, passage turbulence intensity, and mass flow were determined. The rotor exit jet and wake flow were clearly observed as characterized by the passage geometry as well as definite regions of high and low turbulence. The aerodynamic flow characteristics were found to be reasonably independent of rotational speed but highly dependent upon rotor geometry